Thermotransfer sheet material and copying systems utilizing same



March 1966 R. E. MILLER ETAL 3,239,366

THERMOTRANSFER SHEET MATERIAL AND COPYING SYSTEMS UTILIZING SAME FlledNov. 21, 1961 3 Sheets-Sheet 1 WEB BASE COPY RECEIVING SHEET COATED WITHPARTICLES OF SOLID COLOR- REACTANT ADSORBENT MATERIAL INTERMEDIATE SHEETBACK-COATED WITH COMPOSITION CONTAINING SUBLIMABLE DYE PARTICLES MASTERSHEET BEARING HEAT-ABSORBENT GRAPHIC DATA AREAS FIG 2 INFRARED HEAT LAMPINVENTORS ROBERT E. MILLER JAMES K. J. CHENG THEIR ATTORNEYS March 1966R. E. MILLER ETAL 3,239,366

THERMOTRANSFER SHEET MATERIAL AND COPYING SYSTEMS UTILIZING SAME FlledNov. 21. 1961 5 Sheets-Sheet 2 FIG. 4

WEB BASE COPY RECEIVING SHEET COATED WITH PARTICLES OF SOLID 32COLOR-REACTANT ADSORBENT MATERIAL COATING CONTAINING SUBSTANTIALLYCOLORLESS SUBLIMABLE DYE PARTICLES TRANSFER SHEET BEARING HEAT-ABSORBENTGRAPHIC DATA AREAS FIG 5 INFRARED HEAT LAMP INVENTORS ROBERT E. MILLERJAMES K. J. CHENG BYWW W%Wm THEIR ATTORNEYS March 1966 R. E. MILLER ETAL3,239,366

THERMOTRANSFER SHEET MATERIAL AND COPYING SYSTEMS UTILIZING SAME FlledNov. 21, 1961 3 Sheets-Sheet 5 FIG. 7

UNCOATED WEB BASE RECEIVING SHEET COATING CONTAINING SUBLIMABLEPHOTOCHROMIC DYE INTERMEDIATE TRANSFER SHEET MASTER SHEET BEARING HEAT-ABSORBENT GRAPHIC DATA AREAS FG. 8 INFRARED HEAT LAMP FIG.9

ULTRA-VIOLET LAMP INVENTORS ROBERT E. MILLER JAMES K. J. CHENG FACSIMILECOPY THEIR ATTORNEYS United States Patent 3,239,366 THERMOTRANSFER SHEETMATERIAL AND COPYING SYSTEMS UTILIZING SAME Robert E. Miller and JamesKe-Jen Cheng, Dayton, Ohio, assignors to The National Cash RegisterCompany,

Dayton, Ohio, a corporation of Maryland Filed Nov. 21, 1961, Ser. No.153,806 24 Claims. (Cl. 117-36.1)

This invention relates to thermotransfer record copying sheet material,to compositions containing sublimable color-forming compounds usefultherewith, and to graphic data-copying systems utilizing said sheetmaterial.

More particularly, it relates to thermotransfer sheets and to the use ofsuch thermotransfer sheet material coated with sublimable dye, whereby alarge number of duplicate or facsimile copies of a graphic original maybe produced by thermographic means when the thermotransfer dye materialon said transfer sheet is placed in heat-conductive relation with boththe graphic original and a suitable receiving sheet and the combinationis briefly exposed to intense infra-red irradiation obtained withsuitable conventional means.

More specifically, the thermotransfer sheet of this invention isutilized in a copying system in which a master sheet having highheat-absorbent areas containing graphic data and low heat-absorbentareas is irradiated with infrared radiation to control the formation ofan image on a copy-receiving sheet, the image being formed as a coloredimage in the form of a condensed sublimate of normally colorless orslightly colored organic dyes which lead themselves to development to avisibly colored form, in some instances by adsorption reaction in thevapor or solid state with acidic surface active adsorbent material, andin other instances by subjecting the condensed sublimate to lightpredominantly in the ultra-violet region of the spectrum, depending onthe organic compound in use.

Thermographic copying papers and processes have heretofore beeendisclosed, such as the heat-sensitive papers disclosed in United StatesPatent No. 2,710,263, issued to Bryce L. Clark and Carl S. Miller onJune 7, 1955, and the thermographic process disclosed by Carl S. Millerin United States Patent No. 2,740,896, issued April 3, 1956. In theseand similar disclosures, however, there is no disclosure of transfer ofcolor-forming material from a thermotransfer dye-containing material toa receiving sheet as disclosed herein; rather, in such prior-art methodscopies are made on heat-sensitive sheets which are coated with orcontain the color-forming ingredients, by placing a printed or graphicoriginal in heat-conductive contact with said heat-sensitive sheet andthen briefly exposing the graphic original to intense infra-redradiation, thus creating an elevated-temperature pattern in theheatabsorbent graphic matter which is directly conducted to theheat-sensitive layer of the copy sheet to develop a visible copy of thegraphic original on said copy sheet.

7 More recently, there has been disclosed, in United States Patent No.2,939,009, granted to Jack M. Tien on May 31, 1960, a thermal copyingprocess which utilizes the method of making a copy of a graphic originalby thermaltransfer of color-forming compounds coated on a transfer sheetto the surface of a suitably-coated copyreceiving sheet. In general, onedisadvantage associated with the use of such prior-art thermotransfersheets is the relatively small number of copies which can be made withany one transfer sheet. In contrast with the principal disadvantageinherent in such prior-art thermotransfer sheets, the novelthermotransfer materials of the invention provide an unexpectedly largenumber of copies by repeated transfers from the same sheet. From fortyto sixty copies of original data may readily be made with thethermotransfer materials of this invention, the last ICC copy beingessentially of the same quality as the first. As will be made moreapparent hereinafter, the unexpected advantages obtained with thethermotransfer sheet materials of this invention inhere principally inthe thermotransfer composition coated on said sheet material, andparticularly in the thermotransferable sublimable dyes and organiccompounds and mixtures thereof pres ent in said coated compositions.Typical classes of sublimable dyes and organic compounds having thenecessary physical and chemical characteristics to be useful forpurposes of this invention include the following: (1) leuco methyleneblue dyes, (2) leucauramine compounds, and (3) indolino benzo spiropyran compounds. As used herein, in the specification and claims, theterm dye(s) represents and includes any and all of the sublimablecolor-forming compounds disclosed herein. Even though some of thementioned compounds may not normally be considered as dyes, they arecolor-producing, and therefore, from a functional standpoint, they aresimilar to dyes. It has been found that the dyes comprised in thecoating compositions of this invention are transferred or transportedfrom said coating to the surface of the juxtaposed receiving sheet bytrue sublimation. In part, this phenomenon accounts for the large numberof copies obtainable with the novel sheet material, as compared to thelimited number obtainable with related prior-art thermotransfermaterials, in which the color-producing compounds are first melted orfused, so that transport of said prior-art compounds to the receivingsheet surface is effected while the compounds are in the liquid state.Manifestly, a greater number of facsimile copies can be made with thethermotransfer sheet material coated with the sublimable dyecompositions described herein than with prior materials coated withcolor-forming compounds which are transferred in the liquid state,since, for each copy made, other factors being equal, a much smallerfraction of the total available dye or color-forming material istransferred to the receiving sheet by the mechanism of sublimation thanis transferred by liquid transport.

Although the thermotransfer materials of this invention are suitable foruse in a number of different copying systems and arrangements, they arepreferably used in either a two-sheet or a three-sheet arrangement. Inthe two-sheet arrangement, the top sheet consists of a thin flexiblesheet of infra-red-transmitting, base web material bearing on onesurface the graphic data to be copied, the data being present assubstantially heat-absorbent characters, such as black heat-absorbenttypewritten, drawn, or written characters; and having disposed on theother surface of said sheet a thermotransfer coating including one ormore sublimable color-forming dyes. In the production of facsimilecopies, this top sheet is superimposed upon a non-infra-red-absorptivecopy-receiving sheet, and the combination, while held in closeheat-conductive contact, is moved past a source of heat-producingirradiation, such as an infra-red lamp, so that radiant energy is madeto fall on the master sheet at such a rate and at such energy level asto preferentially heat the heat-absorbent printed areas in relation tothe light-reflecting areas having no graphic data. The amount of heatgenera-ted by absorption of radiant energy by the heat-absorbent graphicdata areas is much greater than the amount absorbed by areas where nographic data is present, so that the heat so absorbed results in a heatpattern corresponding to the graphic data. Heat from said heated areas,in the form and outline of said heat pattern, is transferred byconduction through the intervening base web to the dye coating in areascontiguous and corresponding to said graphic data, causing the dye ordyes contained therein to sublime in small quantity, the sublimate soproduced condensing in the form of said heat pattern on the receivingsheet as a colored or latent image, depending on the type of dye andreceiver sheet being used. The color of the image so produced rangesfrom blue to red, the

.color being determined by the particular color-forming It is thereforean object. of this invention to provide a novel therrnotransfer sheetmaterial having on one side a coating comprising at least onesublimable'dye.

Another object of this invention is to provide a novel compositioncomprising at least one color-forming compound useful for coatingthermotransfer sheet material, said compound being sublimable from acoated sheet used for copying purposes with thermographic copying means.Another object of the invention is to the provision of a thermographiccopying system comprising an array of 1) an infra-red-transmitting,low-heat-conductivity master sheet bearing heat-absorbing graphic dataon one surface thereof; (2) an infra-red-transmitting sheet coated onone side with a composition including sublimable color-forming material,and (3) a copy-receiving sheet.

Yet another object of the invention is to provide a thermographiccopying system consisting of two sheets in combination: a first,infra-red-t-ransmitting, sheet having disposed thereon a coatingcontaining a sublimable color-forming compound on one side andheat-absorbent graphic data on the other, and, as a second sheet, acopying-receiving sheet having acidic absorbent particles coated on oneside, which side is in heat-conductive contact with the coated side ofsaid first sheet.

Still another object of the invention is to provide a thermographiccopying system consisting of either a twosheet arrangement or athree-sheet arrangement, wherein said arrangements include one of twospecies of receiving sheet; that is, either a sheet coated withparticles of acid clay absorbent material or like materials, or onewhich consists of a plainsheet of paper with no absorbent coatedthereon, the choice depending on the sublimabledye coated on thetransfer sheet and on the end result desired.

Other objects of the invention will become apparent from the followingdescription and claims and by reference to the accompanying drawings,which disclose the principle of the invention and the best mode ofcarrying out that principle, the drawings and the examples to followbeing merely illustrative and not limitative of the invention.

In the drawings:

FIGS. 1, 2, and 3 represent views, in perspective, of

sheet arrangements for copying graphic data wherein a three-ply stackhaving an intermediate transfer sheet is subjected to infra-redradiation in making a copy.

FIGS. 4, 5, and 6 represent a related arrangement of sheets for copyinggraphic data, except that a twosheet system, instead of the three-sheetarrangement of FIGS. 1, 2, and 3, is shown.

FIGS. 7, 8, 9, and 10 show another system consisting of a three-plyarray of sheets wherein an intermediate sheet coated with a photochromicdye transfers a latent image of graphic data onto a receiving sheet whensaid graphic data is subjected to infra-red radiation, the latent imagebeing developed to a substantially stable visibly infra-red radiationnecessary for the practice of this in FIGS. 1A, 4A, and 7Arepresentcross-sections of the.

sheet arrangements of FIGS. 1, 4,:and 7, respectively. These figures,showing the cross-section of sheetarrangementsin proper relationforconducting. the copying operation, are included to clearly identify theseparate sheets with their associated coated layers; and to-aid'indifferentiating one from the other.

Referring to FIG. 1, there is shown a three-sheet system for copyingheat-absorbent graphic .data,-'consisting of an intermediate sheet 21.,held in heat-conductive contact betweena master sheet 20 and areceiving; sheet 22. The master sheet 20 .is an infra-red-transmittingpaper web base having disposed .on its surface heat-absorbent graphicdata areas 23,'such as carbon ink characters, said master sheet, beingoverlaidin heat-conductive :contact with the uncoated surface of theintermediate sheet'21. The sheet 21 :is'back-coated witha sublimable dyeor a composition containing a :sublimable dye, this coating in turnbeing held in contact with the, coated side of'the receiving sheet 22,which is coatedawith clay particles or equivalent, which particles areacid relative to the sublimable dyes transferred to said sheet. The modeof providing graphic copies. byutilizing a heat pattern as the means fortransferring sublimable dye to a coated receiving sheet using thearrangement of -FIG. 1 was described in detail above.

FIG; 2 shows the three-sheet arrangement of FIG. 1 being brieflyirradiated with an, intense source. of infrared heat-producing raysprovided by a suitable heat lamp. It should be understood that means forproviding suitable vention are nowwell known in the art and hence neednot be describedherein..

FIG. 3 represents the copy-receiving sheet 22 with an exact facsimilecopy 24 of the original graphic data 23.

disposed on the master sheet 20, the: copy having been produced byirradiation of the three-sheet arrangement of FIG. 2.

In FIG. 4, there is shown a combination of two sheets useful for.copying andduplicating graphic originals, con

thin layer of sublimable dye coated onits. bottomsur This transfer sheetISY superposedin heat-conducface. tive contactv relation with thereceiving sheet 31, the contacting surfacev of which is coated withminute particles 1 of surface active adsorbent material, such as thatpreviously described in connection with FIG. 1.

FIG- 5 shows the two-sheet system being exposed to intense infra-redradiation in-the manner described in connection with FIG. .2.

FIG. 6 represents a facsimile copy 33 of graphic original 32 similar tothat described under FIG. 3, except that the copy is made with atwo-sheet system=insteadof the three-sheetsystem of FIG.3.

Referring now to FIG. 7, there is shown, in perspective, a three-sheetcopying system which is identical with the arrangementshown in .FIG. 1except that the receivingv sheet 42'1consists of plain uncoated web basematerial,

and the intermediate transfer sheet 41 is coated with a thin layerincluding a sublimable photochromicidye; The

'sheet 41 is held inheat-condu'ctive contact between said.

receiving sheet and a master sheet 40, whi'ch'master sheet hasheat-absorbent graphic data 43 'disposedon its surface. 1

FIG. 8 shows the three-sheet combination of FIG. 7 being subjectedtohigh-intensity heat rays, such as infrared rays, generated by the heatlamp shown in the figure. In FIG. 9, the uncoated receiving. sheet: 42.is shown with a latent image 44 0f the graphic original on its surfacein position for irradiatiomwith an ultraevioletzlight source, saidlatent image having been obtained by infrared irradiation of thethree-sheet arrangement as shown in FIG. 8. Thus, the latent image 44represents an invisible sublimate of photochromic dye transferred to thereceiving sheet 42 from the intermediate transfer sheet. The latentimage is in the form of the heat pattern generated within the graphicoriginal by irradiation of said original with infra-red rays.

FIG. shows the receiving sheet 42 after exposure to ultra-violet light,the exposure having transformed the latent image 44 to a visibly bluecolored facsimile copy 45 of the graphic original.

It will be apparent that systems which utilize an uncoated receivingsheet are especially useful when used in conjunction with asublimable-photochromic-dye-coated transfer sheet, since one of theprincipal features of this arrangement is to form a latent image of saidphotochromic dye on the surface of the uncoated receiving sheet, whichimage may subsequently be developed to a visibly colored copy of theoriginal graphic data by subjecting the latent image to shortwave-length radiation, such as ultra-violet radiation. A two-sheetsystem utilizing an uncoated receiving sheet in conjunction with asublimable-photochromic-dye-coated master sheet gives essentially thesame result as the three-sheet system and can be substituted therefor.

Other modifications of the arrangement shown in FIGS. 7, 8, 9, and 10are also Within the purview of this invention. For example, when asublimable-photochromic-dyecoated transfer sheet is used with aclay-coated receiving sheet, a visibly colored reddish image Ofthegraphic original is directly obtained on the receiving sheet, instead ofa latent image, which is obtained with the uncoated receiving sheetarrangement above described. It is thus possible to obtain facsimilecopies of graphic data in contrasting colors on the same receiving sheetby the transfer of photochromic dye to clay-coated sheet areas and touncoated sheet areas, the former areas providing a reddish-colored imagedirectly and the latter providing a latent image which develops a bluecolor when subjected to ultra-violet radiation.

Other variations include the use of sublimable dye compositionscomprising sublimable photochromic dyes and one or more of the othersublimable dyes of this invention in a copying system including eitheran uncoated receiving sheet or a clay-coated receiving sheet to obtaingraphic copies of varying color composition.

The following examples are presented in order to provide specificembodiments of compositions comprising sublimable dyes and to set forththe best mode of preparing thermotransfer sheet material including suchcompositions.

EXAMPLE I A preferred composition for coating thermotransfer sheetmaterial of this invention comprises three dyes or color-formingcompounds and is prepared as follows: An aqueous dispersion is preparedby ball-milling a composition consisting of, in parts by weight:

6 parts of 10-isovaleryl-3,7-bis-(dimethylamino) phenothiazine, alsoknown as N-isovaleryl leuco methylene blue, and herein abbreviated asIVLMB,

2.4 parts of N-(2,5 dichlorophenyl) leucauramine,

1.6 parts of a photochromic dye, 1,3,3-trimethyl-5 chloro,

6-nitro, 8' methoxy-spiro[(2H-1-benzopyran) 2,2- indoline] having thestructure 6 3%, based on the combined weight of the dyes, of anonylphenoxyethanol surfactant; i.e., Triton N-100, a non-ionic surfaceactive agent, and 31 parts of water.

This composition is ball-milled for about eighteen hours or until thedye particles have been reduced to an average size of five microns orsmaller. The final transfer coating emulsion is prepared by blending theabove-described dye dispersion with a binder composition consisting of amixture of 2.1 parts (dry weight basis) of a 20% aqueous solution ofElvanol 50-42, a high-viscosity, highly-hydrolyzed polyvinyl alcohol,having a viscosity of 35-45 centipoises when measured with a 4% aqueoussolution at 20 degrees centigrade by the Hoeppler falling ball methodand in which the degree of hydrolysis varies from 97.7 to 98.4%, and1.05 parts (dry weight basis) of Dow Latex 630, which is a 48% solidsstyrene-butadiene copolymer latex. The so-prepared blend is thenadjusted to about 20% total solids, and, after thorough mixing, thedispersion is ready for coating.

A sheet of paper coated with 2.5 pounds per ream (25" x 38 x 500 sheets)of the above composition was used as the thermotransfer sheet in both athree-sheet system and a two-sheet system in accordance with thisinvention, and, when so utilized with thermographic copying means, eachnovel thermotransfer sheet readily provided at least sixty and in manyinstances a greater number of legible and clear facsimile copies of agraphic original on individual attapulgite-clay-coated receiving sheets.

EXAMPLE II The composition of this example consists of twocolorproducing compounds instead of the three shown in Example I. Anaqueous dispersion is prepared by ball-milling the followingingredients, the amounts given as parts by weight:

6.0 parts of l0-isovaleryl-3,7-bis-(dimethyl-amino) phenothiazine, alsodesignated by the trivial name N-isovaleryl leuco methylene blue,

4.0 parts of 1,3,3-trimethyl-5-chloro, 6' nitro, 8' methoxyspiro [(2H-l-benzopyran) -2,2-indoline) 3% based on the combined weight of dyes, ofTriton N- 100, a nonylphenoxyethanol surfactant, the latter being anon-ionic surface active agent, and

31 parts of water After the so-prepared emulsion has been ball-milledfor about eighteen hours, or until the dye particles have been reducedto about five microns, the final coating composition is made by blendingtherewith the binder composition of Example I in the manner describedtherein.

EXAMPLE III In Examples I and II, the coloring materials are dispersedin an aqueous system. In this example, a thermotransfer coatingcomposition consisting of the following materials is prepared, in whichthe materials are dispersed and/or dissolved in an organic vehicle asfollows, all

parts being by weight:

parts of 10 isovaleryl 3,7 bis (dimethylam-ino) phenothiazine,

5 parts of N-(2,5 dichlorophenyl) leucauramine,

4 parts of natural rubber,

0.1 part of lecithin (dispersing agent),

0.03 part of azo-oil Blue Black B, a polyazo alkylated naphthol dye,disclosed in United States Patent No. 2,090,938, issued to Karl F.Conrad on August 24, 1937,

200 parts of straight-chain aliphatic petroleum distillate (boilingrange 205 to 240 degrees Fahrenheit).

Four parts of milled natural rubber is first dissolved in 200 parts ofthe petroleum solvent, to which have been added the given amounts oflecithin, a dispersing agent,

and azo oil Blue Black B," which serves as a tinting agent 'byincorporating a slight color to the coating and thus aids indistinguishing coated areas from uncoated areas of the base sheet. Thecoloring compounds or dyes are then added, and, after thorough mixing,the dispersion is applied as a coating on suitable web stock, such asNekoosa bond paper, in an amount ranging from about two to'three poundsper ream of 25'' x 38 x 500 sheets. The coating is applied to thetransfer base by any suitable conventional technique, and the appliedcoating then is dried by passing the coated medium through a heatedtunnel or the like to evaporate the solvent.

EXAMPLE IV A transfer coating emulsion containing a photochromic dye isprepared by. ball-milling a 3% aqueous dispersion of the photochromicdye of Example I with a 2% aqueous binder solution of DX843-11, apolyethylenemaleic anhydride copolyrner having a specific viscosity of1.0 as a A thermotransfer composition containing the photo- 'chr'omicdye of Example I but having no binder is prepared by evaporating theacetone solvent from a paper base transfer medium coated with asaturated acetone solution of said photochromic dye.

Because of the lower coating weight normally associated with transfersheets prepared in this manner, it is not generally possible to obtainas many copies with these sheets as are obtained with emulsion-coatedbIHdGI'-COI1- taining sheets. In all other respects, however, sheetscoated in the manner of this. example perform in the same manner, withequal adaptability and sensitivity, as the emulsion-coated sheets.

The preferred dyes or color-forming compounds disclosed in the foregoingexamples may be substituted with other compounds selected from the sameor related class of compounds. Examples of compounds from each classwhich have been found to be particularly suitable include the following:

(I) Leuco methylene blue compounds of the formula wherein R is selectedfrom the group consisting of isobutyryl, isovaleryl, pivalyl, acetyl,propionyl, and phenyl acetyl;

(II) Leucauramine compounds of the formula wherein R is selected fromthe group consisting of 2,5 -dichlorophenyl 3,4-ch1orophthaloyl5-ch1oro-2-methylphenyl p-nitrophenyl phenyl, and

, 8; (III) Photochromic'compound of the formula HaC C wherein R R andRare selected from the group consisting of (a) R; is N0 and R and R arehydrogen, (b) R, and R4 are hydrogen and R is N0 (c) R and R arehydrogen and R jis OCH ,(d) R is hydrogen, R is N0 R5 is OCH (e), Rg isCl,-Ri, and R are both N0 (f) R is hydrogen,'R is Br, and R is N0 (g) R,is Cl, R is hydrogen, and R .is N0 (h), R 'is Cl, R

is N0 and R is hydrogen, (i) R is Cl, R is Br, and R is N0 and (j) R 'isCl, R4 is N02, and R is OCH From the foregoing. examples, itis thusapparent that thermotransferable compositions of this invention maycomprise one or more dyes from .eachof the dyes of Groups I, II, and IIIabove, one or more dyes selected. from each of the dyes of Groups I andII or Groups I and III, or one or more dy'es from Group. III.

Although leuco methylene blue compounds substituted in the 10 positionwith v4 and 5 carbon iso-alkyl substituents are not common and wellknown in commerce, such compounds may be prepared ,accordingto the process described in United States Patent No. 2,909,520,=

Compounds of the type shown in Group -II, the leu,

cauramine group, are disclosedinz'United States Letters Patent Nos.2,828,341and 2,828,342,'issued to Clyde S.

Adams et al. on March 25,"1958,.and those of Group 111,?

the indolino benzospiropyran compounds, are disclosed in the UnitedStates patent application of 1Elliot Berman Serial No. 108,710, filedMay 9, 1961, noW=U.S; .Patent. No. 3,100,778 which is acontinuation-in-part of United.

States patent application Serial No. 803,836, 'filed April 3,

1959, and now abandoned.

The acidic adsorbent particles coated on the receiving sheets utilizedwith this invention are vwell known and comprise, preferably,attapulgite clays and zeolite ma-= terials, as Well as many lesspreferred adsorbents. EX.- amples of such ,clays and other adsorbentmaterials; and

sheet materials coated therewith, are disclosed'in United States PatentsNo'.'2,581,186, issued to BarrettK; Green on January 1, 1952;TN0.2,641,557, issued to Barrett K..

Green on June 9, 1953;"and No; 2,777,780, issued to Marjorie J. Cormackand Ned A.- Thacker on January 15, 1957.

Preferably, the polymeric binder material of this in-- Vention comprisea blend of a hydrophilic synthetic polymer and a rubbery copolyrner-latex,.such as the polymer blend of Examples I and II. However, otherpolymeric materials may be substituted for'the preferred bindercompositions. Examples of such other materials 1 include hydrophilicpolyvinyl alcoholwithout the added I copolyrner latex, and hydrophiliccopolymers of: polyethylenemaleic anhydride, as well as other knowncopolymers having similar characteristics. The binder may also comprisepolymers. of natural origin, such as gelatin, gum arabic, and the like.

The. proportions of the three classes. of .dyes may be varied over aconsiderable range.

Preferably, the ratio, on a'weight basis, of the amount of leucomethylene blue dye to the amount of dye from either of the other twoclasses of dyes may vary from about 1.5:1 to 4:1.

From the foregoing, it is manifest that, although the dye proportions ofthe examples are the preferred proportions and yield optimum results,excellent copies are obtainable when the proportions of individual dyesare varied over a wide range.

It should be understood that no criticality lies in the use of anyparticular binder materials or blends thereof, or in any solvent ordispersing agent, and that suitable substitutes and equivalents for theabove classes of materials will be readily suggested to those skilled inthe art. It will also be apparent to skilled artisans that theproportions of these non-critical materials, as well as other variablessuch as coating weight, percent total solids in the coating emulsionsand dispersions, etc., may be adjusted and modified in a mannerconsistent with the desired end result without departing from the scopeof this invention.

Although, in general, all of the dyes enumerated above are stable toheat, only the derivatives of leuco methylene blue are stable to lightand to the effects produced by prolonged exposure to atmosphericconditions. Accordingly, the preferred transfer compositions include aleuco methylene blue derivative, preferably an iso alkyl derivativehaving four or five carbon atoms attached to the 10 position on thephenothiazine group, in combination with one or more dyes from the otherpreviouslydisclosed classes of dyes. Thermotransfer compositionscontaining such leuco methylene blue derivatives provide permanentcopies of graphic matter; i.e., which remain stable indefinitely againstthe effects of heat and light. Some tendency of the graphic copy tofade, however, is observed in copies prepared with sublimable dyecompositions in which leuco methylene blue derivatives have beenexcluded, the degree of fading, of course, varying with the dye and thetype of receiving sheet.

It has been found that graphic copies made on claycoated receivingsheets with thermotransfer sheets coated with the preferred compositionof Example I are clear and legible and exhibit only very slight colorfade even after fifty hours exposure in a standard Fadometer machine.

It will be noted from the foregoing examples that, with the exception ofthe compositions of Examples IV and V, in both of which the onlycolor-forming compound is a photochromic dye, the other compositions allcontain the preferred isovaleryl derivative of leuco methylene blue.Even though this compound is preferred in the compositions of thisinvention, it has been found that a limited number of other derivativesof leuco methylene blue, particularly the lO-isobutyryl and IO-pivalylderivatives, have the proper balance of physical and othercharacteristics, such as melting point and sublimation point, which,when combined in a composition containing at least one other dyeselected from the leucauramine and photochromic dyes of this invention,cooperate with the latter to also provide an unexpectedly large numberof copies when utilized in accordance with the invention.

Although the large number of copies obtainable with transfer sheetscontaining the preferred leuco methylene blue derivatives abovementioned is of great value from a practical and economic standpoint, ithas also been found that other advantages of nearly equal importance areinherent in the use of said derivatives.

For example, a large number of trials have shown that, although thecharacteristic large number of colored facsimile copies of good qualitymay be produced with thermotransfer sheets in which the preferred leucomethylene blue derivatiesi.e., l-isovaleryl, lO-isobutyryl, and10-pivalyl-have been replaced by the other derivatives of this classspecified aboveie, the -acetyl, IO-propionyl, and 10-phenyl acetylderivatives-copies made with sheets containing the former preferredderivatives have much greater stability to color change,

10 show reduced tendency to smudging, and display a more homogeneous andeven distribution of the sublimed dyes than do copies made with sheetscontaining the latter less preferred derivatives.

While the invention has been described with respect to certain preferredembodiments of copying systems and thermotransferable dyes, it should beunderstood that changes in various details of the disclosed inventionmay be made by those skilled in the art without departing from eitherthe spirit or the scope of the invention.

What is claimed is:

1. Thermotransfer record sheet material adapted for making copies ofheat-absorbing graphic data onto receiving sheet material by subjectingsaid graphic data to heat-producing irradiation while said data is heldin heatconductive relation with said thermotransfer and receiving sheetmaterials, the thermotransfer sheet material comprising (1) a flexibleinfra-red-transmitting supporting web base, and

(2) a thin layer containing sublimable dye coated on one side of saidbase, said layer comprising a mixture of sublimable fine solid particlesof (a) a leuco methylene blue dye, (b) a leucauramine compound, and (c)a 1,3,3-trimethyl spiro [(2H'1-benzopyran)-2, 2'-indoline] compound.

2. The thermotransfer sheet of claim 1 wherein (l) the base material isa thin infra-red-transmitting flexible paper web and (2) the thin layeron said base material comprises a polymeric binder having homogeneouslydisperse-d therein a sublimable mixture of fine particles of (a) a leucomethylene blue compound of the formula III-11 2 (CH3) 2N wherein R isselected from the group consisting of:

2,5 -dichlorophenyl 3,4-chlorophtihaloyl 5-chloro-2-methylphenylp-nitrophenyl phenyl and (c) a photochromic spiro-pyran compound of theformula wherein R R and R are selected from the group consisting of (a)R; is N0 and R and R are hydrogen, (b) R, and R are hydrogen and R is N0(c) R and R are hydrogen and R is OCH (d) R is hydrogen, R is N02, R5 isOCH3, (e) R3 is C1, R4 and R5 are N0 (f) R is hydrogen, R is Br, and Ris N0 (g) R is Cl, R is hydrogen and R is N0 (h) R is Cl, R is N0 and Ris hydrogen, (i) R is Cl, R is Br, and R is N0 and (1') R is Cl, R is N0and R is OCH 3. The thermotrans fer sheet material of I claim 2'jwherein (a) the leuco methylene blue compound is I3.

compound of the formula and (c) the photoohromic compound has theformula HaC 4. Thermotransfer record sheet material adapted for makingcopies of heat-absorbing graphic data onto receiving sheet material bysubjecting said graphic data to heat-producing irradiation while saiddata is held in heatconductive relation with said thermotransfer andreceiving sheet materials, the thermotransfer sheet material comprising(1) A flexible infra-red-transmitting supporting Web base, and

(2) A layer containing sublimable dye coated on one side of said base,said layer comprising a mixture of sublimable fine particles of (a) "aleuco methylene blue dye, and (b) a 1,3,3-trimethyl-spiro-[(2H-1'-benzopyran)-2,2'-indoline] compound homogeneously dispersed in abinder. i

5. The thermotransfer sheet of claim 4 wherein the layer coated on thebase material comprises amixture of fine particles of (a) a leucomethylene bluecompound Of the formula (CHa)zN S N(CH3)2 Where R isselected from the group consisting of isobutyryl, isovaleryl, pivalyl,acetyl, propionyl, and phenyl acetyl; and (b) a photochromic compound ofthe formula in 1130 on;

wherein R R4, and R are selected from the group consisting of (a) R is Nand R and R are hydrogen,

, (b) R; and R are hydrogen and R is N0 (0) R and R are hydrogen and Ris OCH- (d) R is hydrogen, R is N0 R is OCH (e) R is Cl, R; and R areboth N0 (f) R is hydrogen, R is Br, and R is N0 (g) R is Cl, R ishydrogen and R is N0 and (h) R; is Cl, R is N0 and R is hydrogen, (i) Ris Cl, R is is OCH3. 6. Thermotransfer record sheetimaterisal adaptedfor making copies of heat-absorbing graphic. dataonto re-:- ceivingsheet material by subjecting said graphic data to heat-producingirradiation while said data is held in heat A 12; "Br' and R is N0=and,(j) R is Cl,

conductive relation with said ,thermotransfer; and receiving sheet;materials, the ,thermotransfer :sheet material comprising (1) A-flexibleinfrared-transmitting supporting web base, and r V i (2) A thin layercontaining sublimable dye coated on one side of said base, said layercomprising amixture of sublimable fine particles of '(a) -a leucomethylene blue dye,'and (b) a leucauramine com pound, said sublimablefine particlesbein-g homogeneoiisly dispersed in a binder;

7. The thermotransfer sheet of claim 6' wherein the layer coated on thebase material comprises a mixture of fine particles of (a) aleuco-methylene blue dye of the formula I r (CH3) 2N. S N (CH3) 2 iwherein sR is selectedfromithegroup consisting of isobutyryl,isovaleryl, pivalyl, acetyl,propionyl, and phenyl acetyl; and (b) aleucauramine compound of the formula:

(CHVa)zN it Nai H92 III-H X B2 wherein ;R is selected from the groupconsisting of:

2,5-dichlorophenyl 3,4-chlorophthaloyl 5-chloro-2-methylphenylp-nitrophenyl phenyl 8. The thermotransfersheet. material oflclaim 7 in-Which the leuco methylene blue compound has the formula: i

0 and the leucauramine compound has the formula 7 CH N i N on a)2 I a):x I

9.:A'thermotransfer :copying system consisting of 2a:

three-sheet array in heat-conductive relation adapted for makingcolored-copies of heat-absorptive graphic matter, comprising, in order,V

(1) an infra-red-transrnitting master sheet having heatabsorptivegraphic data areas on one surface thereof, r V

' (2)1, a flexible non-infra-red-absorptive :thermotransfer f 7 sheetconsisting of a Web base coated on oneside with R; is NOQ, and R5 a thinlayer comprising sublimable dye, said layer comprising a mixture ofsublimable fine solid particles of (a) a leuco methylene blue dye, (b) aleucauramine compound, and (c) a1,3,3-trimethylspiro-[2'H-l'-benzopyran)-2,2'-indoline] compound, and(3) a flexible non-infra-red-absorptive web base receiving sheet coatedon one side with fine particles of acidic adsorbent material, said layerof sublimable dye overlaying said particles of adsorbent material, sothat irradiation of the graphic data areas with infra-red rays ofsuitable duration and energy generates heat in said graphic data areasand, by heat conduction through the supporting web base of sheets 1 and2 above, forms a heat pattern in an area of the dye layer correspondingto the heat-energy-absorbing areas of said graphic data, whereupon saidheat causes a small fraction of sublimable dye in the heated area tosublime and then condense on the receiving sheet acidic particles as avisible colored facsimile of the original graphic data.

10. The thermotransfer copying system of claim 9 in which the coatingcontaining sublimable dye consists of (1) a polymeric binder, and,homogeneously dispersed therein, (2) a sublimable mixture of fineparticles of (a) a leuco methylene blue compound of the formula whereinR is selected from the group consisting of isobutyryl, isovaleryl,pivalyl, acetyl, propionyl, and phenyl acetyl; (b) a leucauraminecompound of the formula III-11 Br II N (CHM and (c) a photochromicspiro-pyran compound of the formula (III) H wherein R R and R areselected from the group consisting of (a) R; is N0 and R and R arehydrogen, (b) R and R are hydrogen and R is N0 (c) R and R are hydrogenand R is OCH (d) R is hydrogen, R is N0 R is OCH (e) R is C1, R and Rare both N0 (f) R;, is hydrogen, R is Br, and R is N0 (g) R is Cl, R ishydrogen and R is N0 (h) R is Cl, R is N0 and R is hydrogen, (i) R isCl, R is Br, and R is N0 and (j) R is Cl, R is N0 and R is OCH 11. Thethermotransfer copying system of claim in Which the coating containingsublimable dye consists of (l) a polymeric binder, and, homogeneouslydispersed therein,

(2) a sublimable mixture of fine particles of (a) the leuco methyleneblue compound is a compound of the formula (I) (ll'Ha 5 0= [JoHz('JCH31O (CHahN \S/ N(CHa)z (b) the leucauramine compound has the formula(CHQZNO @auorm, i I

and (c) the photochromic compound has the formula B OH:

x q 30 c1 5 3 t; 4' 5K 6 l 7/6 NO! 0on3 GHQ sublimable fine solidparticles of (a) a leuco methylene blue dye, (b) a leucauraminecompound, and (c) a l,3,3-trimethyl-spiro-[(2'H-l-benzopyran)-2,2'-indoline] compound, and

(2) a flexible non-infra-red-absorptive web base receiving sheet coatedon one side with fine particles of acidic adsorbent material, saidadsorbent material held in contact with said sublimable dye, so thatirradiation of said graphic areas with infra-red rays of suitableduration and energy generates heat in said graphic areas and by heatconduction through the master sheet supporting web base 1 forms a heatpattern in an area of the dye layer corresponding to theheat-energy-absorbing areas of said graphic data, whereupon said heatcauses a small fraction of sublimable dye in the heated area to sublimeand then condense on the receiving sheet acidic particles as a visiblecolored facsimile of the original graphic data.

13. The thermotransfer copying system of claim 12 wherein the thinsublimable dye layer comprises a polymeric binder having homogeneouslydispersed therein a sublimable mixture of fine particles of (a) a leucomethylene blue compound of the formula (CH3)2N S N(CHa)n wherein R isselected from the group consisting of isobutyryl, isovaleryl, pivalyl,acetyl, propionyl, and phenyl acetyl; (b) a leucauramine compound of theformula wherein R is selected from the group consisting of;-

2,5 -dichlorophenyl 3,4-chlorophthaloyl 5 -chloro-2-methylphenylp-nitrophenyl phenyl and (c) a photochromic spiro-pyran compound of theformula (III) Hio CH3 sisting of (a) R is N and R and R are hydrogen,(b) R and R are hydrogen and R is N0 (c) R and R are hydrogen and R isOCH ((1) R is hydrogen, R4 is N0 R is OCH (e) R is Cl, R and R are bothN0 (f) R is hydrogen, R is Br, and R is N0 (g) R is Cl, R is hydrogenand R is N0 (h) R is Cl, R; l

is N0 and R is hydrogen, (i) R is Cl, R, is Br, and R is N0 and (j) R isCl, R is NO and R is OCH (b) the leucauramine compound has the formulaand (c) the photochromic compound has the formula 15. A thermotr-ansfercopying system consisting of a three-sheet array in heat-conductiverelation adapted for making colored copies of heat-absorptive graphicmatter, comprising, in order,

(1) an infra-red-transmitting master sheet having heatabsorptive graphicdata areas on one surface therei (2 aflexiblenoninfra-red-absorptivetherinotransfer sheet consisting ofa web base coated on one side with 'athinilayer comprising a sublimable indolino benzo spiro pyran dye, and Y(3) a flexible base web receiving sheet,

said layer of sublimable dye overlying said base'web receiving sheet, sothat irradiation of the graphic data areas with infra-red rays ofsuitable duration and energy gene cratesheat in said graphic areas andby heat conduction through the supporting web base of sheets 1 and 2forms a heatpattern in an area of the dye layer corresponding to theheat-energy-absorbing, areas of said graphic data,

whereupon said heat causes a :small fractionof sublimable dye in theheated area to sublime and then condense on the receiving sheet as aninvisible latent image of said graphic data, said latent image beingdeveloped to a distinctive color by brief exposure to, ultra-violetlight.

16. The thermotransfer copying system of claim 15 wherein the sublimabledye is homogeneously dispersed in a polymeric binder coated on saidbase, and said dye is a compound having thecformula (III) 1130 CH:

i CH3 wherein R R4, and R are selected from .the group consisting of (a)R; is .NO andR and R are hydrogen, a (b) R and R are hydrogen and R isN0 (0) R3 and R are hydrogen and R is OCH (d) R is hydrogen, R

is N0 R is OCH (e) Rg is Cl, R4 and R are both 1 N0 (f) R 'is hydrogen,R is Br, and R is N0 (g) R is Cl, R4 ishydrogen and R is-NQ (h) R is Cl,R; is N0 and R is hydrogen, (i) R is Cl, R is Br, and-R is N0 and (j) Ris Cl, R is N0 and R5 is'OCH 17. A thermotransfer copying systemconsisting of a two-sheet array in heat-conductive relation adapted formaking colored copies of heat-absorptive graphic data, comprising, inorder,

(l) a flexible master sheet consisting of an infra-redtransmitting webbase having heat-absorbent graphic data areas disposed on its outersurface, and a thin' layer comprising a sublimable indolino benzo spiropyran dye coated on the opposite surface, and. (2) a flexible base ,webreceiving sheet, said layer of sublimable dye overlaying said base webreceiving sheet, so that irradiation of said graphic areas withinfra-redrays of suitablev duration and energy generates heat in saidgraphic'areas and by heatloonduction through the master sheet supportingweb base 1 forms a heat pattern in an area of'the dye layercorresponding to the, heat-energy-absorbing areas of said graphic data,whereupon said heat causes a small fraction of sublimable dye in theheated area to sublime and then condense on the receiving sheet as aninvisiblelatent image of said graphic data, said latent image beingdeveloped a distinctive color by brief exposure to ultra-violet light.

18.-'The thermotransfer copying system of claim'11' wherein thesublimable dye is homogeneously dispersed in a polymeric binder coatedon said base, and said dye is a compound having the formula HaC whereinR R and R5 are selected from thelgroup con- 17 R and R are hydrogen andR is N (c) R and R are hydrogen and R is OCH ((1) R is hydrogen, R is N0R is OCH (e) R is Cl, R and R are both N0 (f) R is hydrogen, R is Br,and R is N0 (g) R is C1, R is hydrogen and R is N0 (h) R is Cl, R is N0and R is hydrogen, (i) R is Cl, R is Br, and R is N0 and (j) R, is Cl, Ris N0 and R is OCH 19. A thermotransfer copying system consisting of athree-sheet array in heat-conductive relation adapted for making coloredcopies of heat-absorptive graphic matter, comprising, in order,

(1) an infrared-transmitting master sheet having heatalgsorptive graphicdata areas on one surface there- 0 i (2) a flexiblenon-infra-red-absorptive thermotransfer sheet consisting of a web basecoated on one side with a thin layer comprising sublimable dye, saidlayer consisting of a mixture of sublimable fine particles of (a) aleuco methylene blue dye, and' (b) a leucauramine dye, said sublimablefine particles being homogeneously dispersed in a binder, and

(3) a flexible non-infra-red-absorptive web base receiving sheet coatedon one side with fine particles of acidic adsorbent material, said layerof sublimable dye overlaying said particles of adsorbent material, sothat irradiation of the graphic data areas with infra-red rays ofsuitable duration and energy generates heat in said graphic data areasand, by heat conduction through the supporting web base of sheets 1 and2 above, forms a heat pattern in an area of the dye layer correspondingto the heat-energy-absorbing areas of said graphic data, whereupon saidheat causes a small fraction of sublimable dye in the heated area tosublime and then condense on the receiving sheet acidic particles as avisible colored facsimile of the original graphic data.

20. A thermotransfer copying system consisting of a three-sheet array inheat-conductive relation adapted for making colored copies ofheat-absorptive graphic matter, comprising, in order,

( 1) an infra-red-transmitting master sheet having heatabsorptivegraphic data areas on one surface thereof,

(2) a flexible non-infra-red-absorptive thermotransfer sheet consistingof a web base coated on one side with a thin layer comprising sublimabledye, said layer consisting of a mixture of sublimable fine par- 2 ticlesof (a) a leuco methylene blue dye, and (b) a 1,3,3 trimethyl spiro[(2H-1'-benzopyran)-2,2- indoline] compound, said sublimable fineparticles being homogeneously dispersed in a binder, and

(3) a flexible non-infra-red-absorptive web base receiving sheet coatedon one side with fine particles of acidic adsorbent material, said layerof sublimable dye overlaying said particles of adsorbent material, sothat irradiation of the graphic data areas with infra-red rays ofsuitable duration and energy generates heat in said graphic data areasand, by heat conduction through the supporting web base of sheets 1 and2 above, forms a heat pattern in an area of the dye layer correspondingto the heat-energy-absorbing areas of said graphic data, whereupon saidheat causes a small fraction of sublimable dye in the heated area tosublime and then condense on the receiving sheet acidic particles as avisible colored facsimile of the orginal graphic data.

21. A thermotransfer copying system consisting of a three-sheet array inheat-conductive relation adapted for making colored copies ofheat-absorptive graphic matter, comprising, in order,

(1) an infra-red transmitting master sheet having heatabsorptive graphicdata areas on one surface thereof,

(2) a flexible non-infra-red-absorptive thermotransfer sheet consistingof a web base coated on one side with a thin layer comprising sublimabledye, said layer consisting of fine solid particles of a 1,3,3-

trimethyl spiro- (2'H-1'-benzopyran) -2,2'-indoline] compoundhomogeneously dispersed in a binder, and (3) a flexiblenon-infra-red-absorptive web base receiving sheet coated on one sidewith fine particles of acidic adsorbent material, said layer ofsublimable dye overlaying said particles of absorbent material, so thatirradiation of the graphic data areas with infra-red rays of suitableduration and energy generates heat in said graphic data areas and, byheat conduction through the supporting web base of sheets 1 and 2 above,forms a heat pattern in an area of the dye layer corresponding to theheat-energy-absorbing areas of said graphic data, whereupon said heatcauses a small fraction of sublimable dye in the heated area to sublimeand then condense on the receiving sheet acidic particles as a visiblecolored facsimile of the original graphic data.

22. A thermotransfer copying system consisting of a two-sheet array inheat-conductive relation adapted for making colored copies ofheat-absorptive graphic data, comprising, in order,

(1) a flexible master sheet consisting of an infra-redtransmitting webbase having heat-absorbent graphic data areas disposed on its outersurface, and a thin layer comprising sublimable dye coated on theopposite surface ,said layer comprising a mixture of fine particles of(a) a sublimable leuco methylene blue dye, and ('b) a sublimableleucauramine compound, said particles being homogeneously dispersed in abinder, and

(2) a flexible non-infra-red-absorptive web base receiving sheet coatedon one side with fine particles of acidic adsorbent material,

said adsorbent material held in contact with said sub limable dye, sothat irradiation of said graphic areas with infra-red rays of suit-ableduration and energy generates heat in said graphic areas and by heatconduction through the master sheet supporting web base 1 forms a heatpattern in an area of the dye layer corresponding to theheat-energy-absorbing areas of said graphic data, whereupon said heatcauses a small fraction of sublimable dye in the heated area to sublimeand then condense on the receiving sheet acidic particles as a visiblecolored facsimile of the original graphic data.

23. A thermotransfer copying system consisting of a two-sheet array inheat-conductive relation adapted for making colored copies ofheat-absorptive graphic data, comprising, in order,

(1) a flexible master sheet consisting of an infra-redtransmitting webbase having heat-absorbent graphic data areas disposed on its outersurface, and a thin layer comprising sublimable dye coated on theopposite surface, said layer comprising a mixture of fine solidparticles of (a) a leuco methylene blue dye, and (b) a 1,3,3-trimethylspiro [(2H-1'-benzopyran)- 2,2'-indoline] compound, said particles beinghomogeneously dispersed in a binder, and

(2) a flexible non-infra-red-absorptive web base receiving sheet coatedon one side with fine particles of acidic adsorbent material,

said adsorbent material held in contact with said sublimable dye, sothat irradiation of said graphic areas with infra-red rays of suitableduration and energy generates heat in said graphic areas and by heatconduction through the master sheet supporting web base 1 forms a heatpattern in an area of the dye layer corresponding to theheat-energy-absorbing areas of said graphic data, whereupon said heatcauses a small fraction of sublimable dye in the heated area to sublimeand then condense on the receiving sheet acidic particles as a visiblecolored facsimile of the original graphic data.

24. A thermotransfer copying system consisting of a two-sheet array inheat-conductive relation adapted for making colored copies ofheat-absorptive graphic data, comprising, in order,

(l) a flexible master. sheet consisting of aninfra-redcompound, saidparticles. being homogeneously dis-- persed in a binder, and I t (2) aflexible non-infra-red-absorptive web base receiving sheet coated on oneside with fine particles of acidic adsorbent material, said adsorbentmaterial held in contact with said sublimable dye, so that irradiationofsaid graphic areas with infra-red rays of suitable duration and energy.generates heat in said graphic areas and by heat conduction through themaster sheet supporting web base 1 forms a heat patternt'in an area ofthe dye layer corresponding to the heat-energy-absorbingareas of saidgraphic data, -Where-' upon said heat causes a small fraction ofsublimable dye in the heated area to sublime and then condense on thereceiving sheet; acidic particles as a visible colored :facsimile of theoriginal graphic data.

References, Cited byith Examiner- UNITED, STATES PATENTS Murray250'65-.1 Marx i ,'117 36.2 I

Berman et a1. 117-36.2 i "Krantzg 11736.2I Bakanet al; 117-36.2 Franciset al. 117-362 V Harbort 117-362 WILLIAM-D. MARTIN, Priinary'Ex amz ner.

RALPH G. NILSON, RICHARD D. NEVIUS,: r

Examinem.

1. THERMOTRANSFER RECORD SHEET MATERIAL ADAPTED FOR MAKING COPIES OFHEAT-BSORBING GRAPHIC DATA ONTO FRCEIVING SHEET MATERIAL BY SUBJECTINGSAID GRAPHIC DATA TO HEAT-PRODUCING IRRADIATION WHILE SAID DATA IS HELDIN HEATCONDUCTIVE RELATION WITH SAID THERMOSTRANSFER AND RECEIVING SHEETMATERILS, THE THERMOTRANSFER SHEET MATERIAL COMPRISING (1) A FLEXIBLEINFR-RED-TRANSMITING SUPPORT WEB BASE, AND (2) A THIN LAYER CONTAININGSUBLIMABLE DYE COATED ON ONE SIDE OF SAID BASE, SAID LAYER COMPRISING AMIXTURE OF SUBLIMABLE FINE SOLID PARTICLES OF (A) A LEUCO METHYLENE BLUEDYE, (B) A LEUCAURAMINE COMPOUND, AND (C) A 1,3,3-TRIMETHYL - SPIRO -((2''H''1''-BENZOPYRAN)-2,2''-INDOLINE) COMPOUND.